Select the correct inference of the given passage from "The Cask of Amontillado."
"Against the new masonry I re-erected the old rampart of bones. For the half of a century no mortal has disturbed them. In pace requiescat!"
a. Montresor spent fifty years building the wall.
b. Fortunato has never been found.
c. Montresor buried all of the old bones.
d. Fortunato has been sleeping for fifty years.